1. Field of the Invention
This invention relates to a communication terminal device and the method, and more particularly, is applicable to a portable telephone apparatus of the Global System for Mobile communications (GSM) which has been standardized in Europe.
2. Description of the Related Art
In recent years, the diffusion of portable telephone apparatuses is remarkable, and, in proportion to it, a great variety of functions are added to the portable telephone apparatuss. For example, in a portable telephone apparatus of the GSM system described above, if a call incoming from the third party is received when talking, the call in progress and the call newly received can be call-controlled respectively into the desired connecting state (hereinafter, it is referred to as a call waiting service). For instance, the call in progress can be suspended and a newly received call can be connected, or disconnecting the call presently talking and connect with the newly received call, or including the call received among the present call and talk with two parties at the same time, i.e., switching into a tripartite call, or disconnecting the call received and can continue talking with the present call.
The above call controls are executed by performing a predetermined operation determined by a standard in the GSM system. For instance, in case of suspending the call in progress and talk with the call received, "send" key should be pushed after pushing "2" key, and in the case of disconnecting the call in progress and talk with the call received, "send" key should be pushed after pushing the "1" key. Furthermore, to switch into a tripartite call, "3" key should be pushed and then the send key must be pushed, and to disconnect the call received and continue the call in progress "0" key should be pushed and then the send key.
The operating methods of these call controls have been disclosed in detail in the standard literature, "European digital cellular telecommunications system (Phase 2): Man-Machine Interface (MMI) of the Mobile Station (MS) (GSM 02.30)" issued by the European Telecommunication Standard Institute (ETSI).
The aforementioned call waiting service is a very convenient function. However, it cannot necessarily be said that it is a good function in usability from the user's point of view because the numeral to be entered varies depending on the connecting state of a call. Practically, these operating methods of call controls are very difficult to learn for the user, and often cause erroneous operations. It is no problem provided that erroneous operation does not trouble the other party, but if one of the parties were cut off by mistake when switching into a tripartite talk, for example, it causes the other party much trouble.
As a method for solving this problem, it is considered that the user carries a simple handbook explaining call control operating methods with him. However, it does not improve the usability of the user, and it seems that this is not a sufficient solution.